1. Technical Field
The present invention relates to volume rendering, and more particularly to a system and method for maximum/minimum intensity projection.
2. Discussion of Related Art
Maximum Intensity Projection (MIP) is a widely accepted volume rendering technique that is used to extract high-intensity structure from volumetric scalar data. At each pixel the highest sample value encountered along the corresponding viewing ray is determined. MIP is commonly used to extract vascular structure from medical CT or MRI data sets, for example, angiography. MIP exploits the fact, that within angiography data sets the data values of vascular structures are higher than the values of the surrounding tissue. By depicting the maximum data value seen through each pixel, the structure of the vessels contained in the data is captured.
Similarly, the volume rendering technique called Minimum Intensity Projection (MinIP) is used to extract low-intensity structures from volumetric scalar data. At each pixel the lowest data value encountered along the corresponding viewing ray is determined. MinIP is often used for lungs and airways studies. MIP and MinIP are opposite methods from algorithms point of view. By reversing the maximum and minimum theses algorithms are mirror symmetric.
Ray casting based MIP is intrinsically expensive since the rays must go through and tri-linearly interpolate all the samples along them to find the maximal values. The commonly used acceleration techniques for direct volume rendering of raycast such as space leaping and early ray termination can not be used for MIP.
Therefore, a need exists for a system and method for MIP/MinIP having improved speed characteristics.